1. Field of the Invention (Technical Field)
This invention relates to apparatuses for measurement of analytes injected into a static electrochemical cell and a method for its use.
2. Background Art
Several different techniques for measurement of analyte concentration have evolved in the prior art. Notable among these techniques is flow injection analysis (FIA). In this measurement process, a sample to be analyzed is injected into a laminarly flowing carrier stream of solvent and reagents. Reproducible sample volumes are injected, so the reaction need not proceed to the steady state. The reaction is developed only to the point which permits recordation as the sample passes an appropriate detector. The output transient signals thus produced reflect the concentration of the injected analyte. Flow injection analysis is described in articles entitled "Flow Injection Analysis: New Tool for Old Assays--New Approach to Analytical Measurements," by Kent K. Stewart (Analytical Chemistry, Vol. 55, No. 9, Aug. 1983) and "Flow Injection Analysis: From Test Tube to Integrated Microconduits," (Analytical Chemistry, Vol. 55, No. 11, Sep. 1983); and in the Lachat brochure entitled "The FIA Concept.," the Tecator brochure on the FIAstar Flow Injection Analysis Bibliography., and the Control Equipment Corporation brochures entitled "The Applications: What it Does."
Obvious disadvantages are present with flow injection analysis. Pumps, valves, and tubing are required. Further, chemical reaction is often required to convert the analyte to a detectable species.
Other quantitative analysis apparatuses are taught by the prior art. U.S. Pat. No. 4,865,992, entitled System and Method for Quantitative Analysis of a Solution, to Hach, et al., teaches such apparatus comprising continuous addition of reagent to a beaker containing a chemical species to be measured until an endpoint is reached. This procedure requires a chemical reaction, large samples, and involves a slow measurement of reaction product.
U.S. Pat. No. 4,695,555, entitled Liquid Chromatographic Detector and Method, to O'Keeffe, involves "spray electrification" wherein droplets of an analyte acquire electric charges dependent upon the concentration of solute carried by the droplet. Measurement of concentration of solute is enabled by measurement of the amount of deviation of the droplets from a neutral path. U.S. Pat. No. 4,003,705, entitled Analysis Apparatus and Method of Measuring Rate of Change of Electrolyte pH, to Buzza. et al., teaches specific measurements of CO.sub.2 and chloride in blood, based on reaction with an electrolyte and subsequent pH measurement.
International Application No. PCT/DK89/00070. entitled A Method of Effecting NIR-Analyses of Successive Material Samples, and a System for Carrying Out the Method, to Johnsen, discloses a near-infrared reflection spectroscopy apparatus wherein the effect of remnant deposits is avoided by an advancing film between test chamber and optical unit.
Thus, it is seen that the prior art lacks a fast, repetitive, highly reproducible, versatile, and reliable analytical measurement system devoid of conduits, valves, and pumps.